JP4720562B2 - Coextruded multilayer film and packaging material using the film - Google Patents

Coextruded multilayer film and packaging material using the film Download PDF

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JP4720562B2
JP4720562B2 JP2006074154A JP2006074154A JP4720562B2 JP 4720562 B2 JP4720562 B2 JP 4720562B2 JP 2006074154 A JP2006074154 A JP 2006074154A JP 2006074154 A JP2006074154 A JP 2006074154A JP 4720562 B2 JP4720562 B2 JP 4720562B2
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multilayer film
resin
film
density polyethylene
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JP2007245612A (en
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正昭 小林
弘明 松原
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Dic株式会社
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Description

  The present invention relates to a packaging material for packaging foods, medicines, medical instruments, industrial parts, miscellaneous goods, magazines, etc., and in particular, tearability by hand is good not only in the vertical direction of the film but also in the horizontal direction, The present invention also relates to a coextruded multilayer film having heat seal strength that can be easily opened by hand, and a packaging material comprising the film.

  Conventionally, a packaging material is required to have high heat seal strength and pinhole resistance from the viewpoint of protecting contents. On the other hand, in the recent trend of emphasizing universal design, easy-openability that can be easily opened by hand is required as a consideration for the socially vulnerable (elderly, infants, disabled, etc.). Easy-openability means the ability to be easily opened by hand without using an opening jig such as scissors or a knife. As a method for imparting easy-openability, (1) a method of making the film easy to tear in the longitudinal direction or the lateral direction (hereinafter referred to as “easy-cut property”), and (2) a heat seal portion of the packaging material having an appropriate heat. Although there is a method of making the heat seal part easy to peel off so as to have a sealing strength (hereinafter referred to as “easy peel property”), conventionally, it provides either easy-cut property or easy peel property. As a result, easy opening was realized.

  However, in the case of a packaging material having easy-cutting properties, there are cases where opening is not easy when there is no cut (notch) that facilitates tearing or when the cut is insufficient. On the other hand, in the case of packaging materials with easy peel properties, when the tab portion (opening opening) of the handle is too small, or when the heat seal strength is increased to prevent bag breakage during sterilization or logistics transportation When the consumer actually uses it, it may not be opened easily. In addition, packaging materials such as medical instruments used in the medical field cannot be reliably opened in a short time, which may cause a life-threatening emergency and become a serious problem. Therefore, even if there is no opening jig etc., it can be easily opened by hand, and there are two or more opening methods, and even if it cannot be opened easily by one opening method, it can be easily opened by the other opening method. There is a need to be able to do it. Therefore, in recent years, a packaging material having both easy-cutting properties and easy peel properties has become necessary so that it can be opened more reliably under any circumstances.

  In order to solve the above problems, the first layer formed from a cyclic olefin resin composition mainly composed of a cyclic olefin resin and an olefin (co) polymer or a composition containing the first layer is formed. Further, a polyolefin-based multilayer laminate in which at least two layers with the second layer are laminated has been proposed (for example, see Patent Document 1). In this polyolefin-based multilayer laminate, the thickness of the first layer formed from the cyclic olefin-based resin composition is as thick as 70% (70 μm) of the thickness of the multilayer laminate, and the second layer is rigid. Since a high-polypropylene resin is used, the flexibility is poor and the pinhole resistance to bending is problematic. Furthermore, since such a highly rigid resin is used, when the thickness of the multilayer laminate is 100 μm or more, tearing by hand is difficult for children and elderly people, and it is easy to cut. There was a problem that could not be obtained. Moreover, although the interlayer adhesion (heat seal strength) is increased, the easy peel property is not considered, and the easy-openability is not sufficient.

A packaging film in which a layer made of an alicyclic structure-containing polymer and a layer made of another thermoplastic resin are laminated has been proposed. (For example, refer to Patent Document 2). Since this packaging film is as thin as 20 to 40 μm, it is relatively easy to cut. However, even in this packaging film, although the interlayer adhesion is improved, the easy peel property is not considered, and the easy-opening property is not sufficient. In addition, since the outer layer is made of high-rigidity polypropylene or high-density polyethylene in the same manner as the above-described polyolefin-based multilayer laminate, the flexibility is poor and pinhole resistance is problematic.
JP-A-8-72210 JP 2000-334890 A

  The object of the present invention is to have two types of easy-opening properties: easy cutability that allows easy tearing in both the vertical and horizontal directions of the film, and easy peelability that allows the heat-sealed portion to be easily peeled off. Another object of the present invention is to provide a coextruded multilayer film that can be secondarily molded and can withstand pinhole resistance caused by bending, and a packaging material using the film.

As a result of intensive studies, the present inventors have found that a resin layer (A) using low-density polyethylene and / or linear low-density polyethylene, low-density polyethylene and / or linear low-density polyethylene, and cyclic olefin resin And a resin layer (C) using low-density polyethylene and / or linear low-density polyethylene and a butene-1 polymer, (A) / (B) / The three-layer or four-layer multilayer film formed by the coextrusion lamination method in the order of (C) or in the order of (A) / (B) / (A) / (C) is easy to cut and easy peel. It has been found that it is excellent, can be secondarily molded, and has excellent pinhole resistance due to bending, and the present invention has been completed.

  That is, the present invention relates to a resin layer (A) comprising a low density polyethylene (a1) and / or a linear low density polyethylene resin (a2), a low density polyethylene (b1) and / or a linear low density polyethylene resin. (B2) 70 to 90% by mass of resin layer (B) containing 10 to 30% by mass of cyclic olefin resin (b3), low density polyethylene resin (c1) and / or linear low density polyethylene resin ( c2) A resin layer (C) containing 70 to 90% by weight and 10 to 30% by weight of a butene-1 polymer (c3), in the order of (A) / (B) / (C), or ( A coextruded multilayer film characterized by being laminated in the order of A) / (B) / (A) / (C) and a packaging material using the film.

  The co-extruded multilayer film of the present invention has two types of easy-opening properties: easy cutability that allows easy tearing in both the vertical and horizontal directions, and easy peelability that allows easy peeling of the heat seal portion. Therefore, it is possible to provide a packaging material that can be easily opened even by a socially vulnerable person. It also has excellent secondary moldability and resistance to pinholes caused by bending. Therefore, the coextruded multilayer film of the present invention is suitable for a packaging material for packaging foods, medicines, medical instruments, industrial parts, miscellaneous goods, magazines and the like. In particular, since it has two types of easy-openability, easy-cut property and easy-peel property, it can be reliably opened in a short time, and is therefore very useful as a packaging material for medical instruments.

  The low density polyethylene (a1), (b1) and (c1) used in the resin layers (A), (B) and (C) of the coextruded multilayer film of the present invention are branched low density obtained by a high pressure radical polymerization method. Polyethylene may be used, and branched low-density polyethylene obtained by homopolymerizing ethylene by a high-pressure radical polymerization method is preferable. Since such low density polyethylene has low mechanical strength, it is relatively brittle compared to other olefin resins and has good tearability, and also has good compatibility with the cyclic olefin resin (b2). Transparency can also be maintained. Furthermore, the adhesive strength between the resin layer (A) and the resin layer (B) can be maintained without using an adhesive resin or an adhesive, and since it has flexibility, it has pinhole resistance. It becomes good.

The low density polyethylene is preferably one density of 0.900~0.935g / cm 3, it is more preferred 0.915~0.930g / cm 3. If the density is within this range, it has appropriate rigidity, excellent mechanical strength such as pinhole resistance, and film film formability and extrusion suitability are improved.

  The low density polyethylene has a melt flow rate (measured at 190 ° C. and 21.18 N in accordance with JIS K7210; hereinafter referred to as “MFR”) of 0.1 to 10 g / 10 min. Is preferable, 0.3 to 8.0 g / 10 min is more preferable, and 0.8 to 6.0 g / 10 min is particularly preferable. When the MFR is within this range, the extrusion moldability of the film is improved.

  Further, the low density polyethylene preferably has a melt tension (melt tension; hereinafter referred to as “MT”) of 4 to 15, more preferably 5 to 13. When MT is within this range, secondary formability and pinhole resistance are improved. The MT is a value measured using a melt tension tester (for example, manufactured by Toyo Seiki Seisakusho Co., Ltd.). After the low-density polyethylene is heated to 190 ° C. in the same apparatus, the resin is discharged from a 2 mmφ nozzle. It is obtained by forming an extruded strand at 0.75 ml / min in an atmosphere of 23 ° C., and measuring the tension when the strand is drawn at a speed of 25 to 60 m / min with an air gap of 90 cm.

When linear low density polyethylene is used instead of the low density polyethylene in the resin layers (A), (B) and (C) of the coextruded multilayer film of the present invention, pinhole resistance and hot tack resistance are improved. Furthermore, even if each resin layer is thinned, sufficient mechanical strength can be obtained, and film rigidity can be improved. The linear low density polyethylene (a2), (b2) and (c2) used for the resin layers (A), (B) and (C) were produced by a metallocene catalyst among linear low density polyethylenes. An ethylene-butene-1 copolymer is preferred. When a normal grade linear low density polyethylene is used, the mechanical strength is higher than that of the low density polyethylene, so that the easy-cut property may be insufficient, but the ethylene produced by this metallocene catalyst -By using a butene-1 copolymer, sufficient easy cutting properties can be obtained. The ethylene-butene-1 copolymer produced with the metallocene catalyst preferably has a density of 0.916 to 0.950 g / cm 3 , more preferably 0.919 to 0.940 g / cm 3 . When the density is within this range, sufficient mechanical strength (impact resistance) is obtained, and the film rigidity is sufficient. The MFR (190 ° C., 21.18N) is preferably 2 to 10 g / 10 minutes, more preferably 3 to 7 g / 10 minutes. When the MFR is within this range, the extrusion moldability of the film is improved. Further, the content of the butene-1 monomer in the ethylene-butene-1 copolymer produced by the metallocene catalyst is preferably 0.5 to 10 mol%, more preferably 1 to 5 mol%.

  In the resin layers (A), (B) and (C) of the coextruded multilayer film of the present invention, the low density polyethylene and the linear low density polyethylene may be used in combination. When low density polyethylene and linear low density polyethylene are used in combination, it is possible to improve easy cutability, pinhole resistance, hot tack property and film rigidity, respectively. When the low density polyethylene (hereinafter referred to as “LDPE”) and the linear low density polyethylene (hereinafter referred to as “LLDPE”) are used in combination, the content ratio of both is LDPE: LLDPE = 95: 5. The range of -40: 60 is preferable, and the range of 90: 10-50: 50 is more preferable. When the content ratio of LDPE and LLDPE is within this range, easy-cut property, pinhole resistance, hot tack property and film rigidity are improved.

  Examples of the cyclic olefin resin (b2) used in the resin layer (B) of the coextruded multilayer film of the present invention include a norbornene polymer, a vinyl alicyclic hydrocarbon polymer, a cyclic conjugated diene polymer, and the like. . Among these, norbornene-based polymers are preferable. The norbornene-based polymer includes a ring-opening polymer of a norbornene-based monomer (hereinafter referred to as “COP”), a norbornene-based copolymer obtained by copolymerizing a norbornene-based monomer and an olefin such as ethylene (hereinafter, referred to as “COP”). , “COC”). Furthermore, COP and COC hydrogenates are particularly preferred. In addition, the weight average molecular weight of the cyclic olefin resin (b2) is preferably 5,000 to 500,000, more preferably 7,000 to 300,000.

The norbornene polymer and the norbornene monomer used as a raw material are alicyclic monomers having a norbornene ring. As such a norbornene-based monomer, for example,
Examples thereof include norbornene, tetracyclododecene, ethylidene norbornene, vinyl norbornene, ethylidetetracyclododecene, dicyclopentadiene, dimethanotetrahydrofluorene, phenylnorbornene, methoxycarbonylnorbornene, methoxycarbonyltetracyclododecene and the like. These norbornene monomers may be used alone or in combination of two or more.

  The norbornene-based copolymer (COC) is obtained by copolymerizing an olefin copolymerizable with the norbornene-based monomer. Examples of such olefin include ethylene, propylene, and 1-butene. Examples thereof include olefins having 2 to 20 carbon atoms; cycloolefins such as cyclobutene, cyclopentene, and cyclohexene; non-conjugated dienes such as 1,4-hexadiene. These olefins can be used alone or in combination of two or more.

  In addition, the content ratio of the norbornene monomer in the norbornene copolymer (COC) is preferably 40 to 90 mol%, more preferably 50 to 80 mol%. If the content ratio is in this range, the film rigidity, tearability, and processing stability are improved.

  Examples of commercially available products that can be used as the cyclic olefin-based resin (b2) include ring-opening polymers (COP) of norbornene-based monomers, such as “ZEONOR” manufactured by Nippon Zeon Co., Ltd., and norbornene-based resins. Addition polymers (COC), for example, “Apel” manufactured by Mitsui Chemicals, Inc., “TOPAS” manufactured by TICONA, and the like can be mentioned.

  The content ratio of the low-density polyethylene (b1) and / or linear low-density polyethylene (b2) in the resin layer (B) and the cyclic polyolefin-based resin (b3) is (b1) and / B (b2) :( b3) = 70: 30 to 90:10, more preferably (b1) and / or (b2) :( b3) = 80: 20 to 90:10. If the content ratio of each resin is within this range, the transparency is improved, and the ease of cutting in the vertical and horizontal directions and the interlayer adhesive strength between the resin layers (A) and (C) are improved.

  The resin layer (C) of the coextruded multilayer film of the present invention serves as a heat seal layer, but the butene-1 polymer (c3) used for the resin layer (C) is a butene-1 homopolymer or butene- A resin having 1 as a main component and copolymerized with ethylene or propylene. As content of the butene-1 monomer in a butene-1 type polymer, 60-100 mol% is preferable and 70-100 mol% is more preferable. Further, the melting point of the butene-1 polymer (c3) is preferably in the range of 70 to 120 ° C. If melting | fusing point is this range, blocking of films can be prevented and it is excellent in low temperature heat-sealing property.

  The content ratio of the low density polyethylene (c1) and / or the linear low density polyethylene (c2) and the polybutene-1 (c3) in the resin layer (C) is (c1) and / or Or (c2) :( c3) = 70: 30 to 90:10, more preferably (c1) and / or (c2) :( c3) = 75: 25 to 90:10. If the content ratio of each resin is within this range, transparency is improved and an appropriate heat seal strength is obtained.

  The coextruded multilayer film of the present invention is a multilayer film having a three-layer structure in which the resin layers (A), (B) and (C) are laminated in the order of (A) / (B) / (C), or ( A multilayer film having a four-layer structure laminated in the order of A) / (B) / (A) / (C). The thickness of the resin layer (B) in this multilayer film is preferably 20 to 60%, more preferably 20 to 50%, of the thickness of the coextruded multilayer film. When the ratio of the thickness of the resin layer (B) to the thickness of the coextruded multilayer film is within this range, the transparency, tearability, and pinhole resistance are improved.

  Furthermore, the coextruded multilayer film of the present invention preferably has a thickness of 50 to 300 μm. If the thickness of the multilayer film is 80 μm or more, excellent secondary formability can be obtained. Moreover, in the range whose thickness of a multilayer film is 50-80 micrometers, it can be used as a bag-shaped packaging material which heat-sealed resin layers (C). Furthermore, even if the coextruded multilayer film of the present invention is a thick film having a thickness of 100 to 300 μm, it is excellent in linear cut property and tear property.

  In the resin layers (A), (B) and (C), an antifogging agent, an antistatic agent, a thermal stabilizer, a nucleating agent, an antioxidant, a lubricant, an antiblocking agent, a release agent are optionally provided. Components such as an agent, an ultraviolet absorber and a colorant can be added within a range that does not impair the object of the present invention. In particular, the resin layer (A) and (C) preferably have a friction coefficient of 1.5 or less, more preferably 1.2 or less in order to impart processing suitability during film forming and packaging suitability of the filling machine. It is preferable to add a lubricant or an antiblocking agent to the layers (A) and (C) as appropriate.

  Although it does not specifically limit as a manufacturing method of the coextrusion multilayer film of this invention, For example, the low density polyethylene (a1) and / or linear low density polyethylene (a2) used for a resin layer (A), and a resin layer ( B) low density polyethylene (b1) and / or linear low density polyethylene (b2) and cyclic olefin resin (b3) used for the resin layer (C) and / or low density polyethylene resin (c1) and / or The linear low density polyethylene resin (c2) and the butene-1 polymer (c3) are heated and melted in separate extruders, and are melted by a method such as a coextrusion multilayer die method or a feed block method. After laminating in the order of (A) / (B) / (C) or in the order of (A) / (B) / (A) / (C), it is formed into a film by inflation, T-die chill roll method, etc. You Coextrusion methods. This coextrusion method is preferable because the thickness ratio of each layer can be adjusted relatively freely, and a multilayer film excellent in hygiene and cost performance can be obtained. Furthermore, since the difference in softening point (melting point) between the low density polyethylene resin and the cyclic olefin resin used in the present invention is large, phase separation or gel may occur. In order to suppress the occurrence of such phase separation and gel, the T-die / chill roll method capable of performing melt extrusion at a relatively high temperature is preferable.

  Since the coextruded multilayer film of the present invention is obtained as a substantially unstretched multilayer film by the above production method, secondary molding such as deep drawing by vacuum molding becomes possible.

  The coextruded multilayer film of the present invention can be used as a sealant film, and a substrate can be laminated on the resin layer (A) via an adhesive resin or adhesive to form a laminate film. The base material used for the laminate film is not particularly limited as long as it does not impair easy-cutability. For example, biaxially stretched polypropylene (OPP) and ethylene vinyl alcohol copolymer (EVOH) are used as the central layer. Coextruded biaxially oriented polypropylene, biaxially oriented ethylene vinyl alcohol copolymer (EVOH), coextruded biaxially oriented polypropylene coated with polyvinylidene chloride (PVDC), biaxially oriented nylon, biaxially oriented polyethylene terephthalate, aluminum foil, etc. Is mentioned. Examples of the bonding method include dry lamination, wet lamination, non-solvent lamination, extrusion lamination, and the like.

  Examples of the adhesive used in the dry lamination include a polyether-polyurethane adhesive and a polyester-polyurethane adhesive.

  Furthermore, in order to improve the adhesiveness with the printing ink and the suitability for lamination, it is preferable to subject the resin layer (A) to a surface treatment. Examples of such surface treatment include corona treatment, plasma treatment, chromic acid treatment, flame treatment, hot air treatment, surface oxidation treatment such as ozone / ultraviolet treatment, and surface unevenness treatment such as sandblasting. Corona treatment is preferable.

  Examples of the packaging material comprising the coextruded multilayer film of the present invention include packaging bags and packaging containers used for foods, medicines, medical instruments, industrial parts, miscellaneous goods, magazines and the like.

  The packaging bag is a packaging bag formed by heat-sealing the resin layers (C) by using the resin layer (C) of the coextruded multilayer film of the present invention as a heat seal layer. Cut the two coextruded multilayer films into the desired size of the packaging bag, overlap them and heat-seal three sides to form a bag, and then remove the contents from one side that is not heat-sealed. After filling, it can be heat sealed and used as a packaging bag. Moreover, it can be used also in the form of pillow packaging using a single sheet of the coextruded multilayer film. Furthermore, it is also possible to form a packaging bag by heat-sealing another resin layer (C) and another heat-sealable film. At that time, as another film to be used, a film such as LDPE or EVA having relatively low mechanical strength can be used. In addition, a laminate film in which a film such as LDPE or EVA and a stretched film having relatively good tearability, for example, a biaxially stretched polyethylene terephthalate film (OPET), a biaxially stretched polypropylene film (OPP), or the like, is used. Can do.

  The packaging container includes a deep-drawn molded product (bottom material having an opening at the top) obtained by secondary molding of the coextruded multilayer film of the present invention. A bottom material is mentioned. The lid material for sealing the bottom material is not particularly limited as long as it can be heat-sealed with the bottom material. However, since the lid material and the bottom material can be simultaneously torn and opened, the coextruded multilayer film of the present invention is covered with the lid material. It is preferable to use as.

  Examples of the secondary forming method include a vacuum forming method, a pressure forming method, and a vacuum / pressure forming method. Among these, vacuum forming is preferable because a film or sheet can be formed in-line on a packaging machine and filled with the contents.

  The packaging material using the coextruded multilayer film of the present invention has an arbitrary tear start portion such as a V-notch, an I-notch, a perforation, and a micro-porosity in the seal portion in order to weaken the initial tear strength and improve the openability. Is preferably formed.

  Next, the present invention will be described in more detail with reference to examples and comparative examples.

Example 1
As a resin for the resin layer (A), low density polyethylene (“UBE polyethylene F109” manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.918 g / cm 3 , MFR: 2 g / 10 min (190 ° C., 21.18 N), MT : 10 g; hereinafter referred to as “LDPE”), as resin for the resin layer (B), 80 parts by mass of LDPE and a cyclic olefin copolymer (“ZEONOR 1060R” manufactured by Nippon Zeon Co., Ltd., MFR: 60 g / 10 minutes) (280 ° C., 21.18 N), glass transition temperature: 100 ° C .; hereinafter referred to as “COP”) Using 20 parts by mass of mixed resin, as resin for resin layer (C), 90 parts by mass of LDPE and polybutene-1 ( BASELL Inc. "8240", density: 0.91g / cm 3, MFR: 2g / 10 min (190 ℃, 21.18N); hereinafter, "PB 1 "hereinafter.) With 10 parts by weight mixed resin.

  These resins are supplied to an extruder for a resin layer (A) (caliber 50 mm), an extruder for a resin layer (B) (caliber 50 mm) and an extruder for a resin layer (C) (caliber 40 mm), respectively. After melting at 230 ° C., each film is supplied to a T-die / chill roll co-extruded multilayer film production apparatus (feed block and T-die temperature: 250 ° C.) having a feed block to perform co-melt extrusion, and the layer structure of the film Was a three-layer structure of (A) / (B) / (C), and a coextruded multilayer film having a thickness of 60 μm / 50 μm / 10 μm (total of 120 μm) was obtained.

(Example 2)
The thickness of each layer of the film is (A) / (B) in the same manner as in Example 1 except that a mixed resin of 70 parts by mass of LDPE and 30 parts by mass of PB-1 was used as the resin for the resin layer (C). / (A) = 60 μm / 30 μm / 30 μm (total 120 μm) was prepared as a co-extruded multilayer film to obtain a co-extruded multilayer film.

(Example 3)
As a resin for the resin layer (A), an ethylene-butene-1 copolymer produced by a metallocene catalyst (“ZM039” manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.93 g / cm 3 , MFR: 4 g / 10 minutes) (190 ° C., 21.18 N); hereinafter referred to as “LLDPE”), as a resin for the resin layer (B), a mixed resin of 80 parts by mass of LLDPE and 20 parts by mass of COP is used as a resin for the resin layer (C). The thickness of each layer of the film was (A) / (B) / (C) = 60 μm / 50 μm in the same manner as in Example 1 except that 70 parts by mass of LLDPE and 30 parts by mass of PB-1 were used. A coextruded multilayer film was prepared so as to be / 10 μm (120 μm in total) to obtain a coextruded multilayer film.

Example 4
As resin for resin layer (A), a mixed resin of 70 parts by weight of LDPE and 30 parts by weight of LLDPE is used, and as a resin for resin layer (B), a mixed resin of 50 parts by weight of LDPE, 30 parts by weight of LLDPE and 20 parts by weight of COP is used. The thickness of each layer of the film is (A) / (B) / () in the same manner as in Example 1 except that a mixed resin of 70 parts by weight of LDPE and 30 parts by weight of PB-1 was used as the resin for (C). C) = 60 μm / 30 μm / 30 μm (a total of 120 μm) was prepared as a coextruded multilayer film to obtain a coextruded multilayer film.

(Example 5)
LDPE is used as the resin for the resin layer (A), 80 parts by mass of LDPE and 20 parts by mass of COP are used as the resin for the resin layer (B), and 70 parts by mass of LDPE and PB- are used as the resin for the resin layer (C). 1 30 parts by mass of mixed resin was used.

  These resins are supplied to an extruder for a resin layer (A) (caliber 50 mm), an extruder for a resin layer (B) (caliber 50 mm) and an extruder for a resin layer (C) (caliber 40 mm), respectively. After melting at 230 ° C., each film is supplied to a T-die / chill roll co-extruded multilayer film production apparatus (feed block and T-die temperature: 250 ° C.) having a feed block to perform co-melt extrusion, and the layer structure of the film (A) / (B) / (A) / (C), and a co-extruded multilayer film having a thickness of 60 μm / 30 μm / 10 μm / 20 μm (total of 120 μm) was obtained.

(Example 6)
A mixed resin of 70 parts by weight of LDPE and 30 parts by weight of LLDPE was used as the resin for the resin layer (A), and a mixed resin of 50 parts by weight of LDPE, 30 parts by weight of LLDPE and 20 parts by weight of COP was used as the resin for the resin layer (B). In the same manner as in Example 5, the thickness of each layer of the film was (A) / (B) / (A) / (C) = 60 μm / 30 μm / 10 μm / 20 μm (total 120 μm). A film was prepared to obtain a coextruded multilayer film.

(Example 7)
Implemented except that LLDPE 90 parts by mass and COP 10 parts by weight of mixed resin were used as the resin layer (B) resin, and LLDPE 70 parts by weight and PB-1 30 parts by weight of mixed resin were used as the resin layer (C) resin. In the same manner as in Example 1, a coextruded multilayer film was prepared so that the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 10 μm / 10 μm (total 30 μm). A multilayer film was obtained. Next, the surface of the resin layer (A) of the coextruded multilayer film was subjected to corona discharge treatment so that the surface energy was 36 mN / m.

  A biaxially stretched polyethylene terephthalate film (thickness 12 μm) was bonded to the surface of the resin layer (A) of the coextruded multilayer film obtained above by dry lamination to obtain a laminate film. At this time, as a dry lamination adhesive, a two-component curable adhesive (polyester adhesive “LX63F” and a curing agent “KP90”) manufactured by Dainippon Ink & Chemicals, Inc. was used.

(Comparative Example 1)
Implemented except that the resin for the resin layer (B) was a mixed resin of 92 parts by mass of LDPE and 8 parts by mass of COP, and the resin for the resin layer (C) was a mixed resin of 70 parts by mass of LDPE and 30 parts by mass of PB-1. In the same manner as in Example 1, a coextruded multilayer film in which the thickness of each layer of the film was (A) / (B) / (C) = 60 μm / 50 μm / 10 μm (total 120 μm) was obtained.

(Comparative Example 2)
The thickness of each layer of the film is (A) / (B) / (C in the same manner as in Comparative Example 1 except that a mixed resin of LDPE 60 parts by mass and COP 40 parts by mass is used as the resin for the resin layer (B). ) = 60 μm / 50 μm / 10 μm (total 120 μm) was obtained.

(Comparative Example 3)
The thickness of each layer of the film is (A) / (B) in the same manner as in Example 1 except that a mixed resin of 60 parts by mass of LDPE and 40 parts by mass of PB-1 was used as the resin for the resin layer (C). / (C) = 60 μm / 50 μm / 10 μm (total of 120 μm) was prepared as a coextruded multilayer film to obtain a coextruded multilayer film.

(Comparative Example 4)
Except that LLDPE was used as the resin for the resin layer (A), a mixed resin of 80 parts by mass of LDPE and 20 parts by mass of COP was used as the resin for the resin layer (B), and LDPE was used as the resin for the resin layer (C). In the same manner as in Example 1, a coextruded multilayer film was prepared so that the thickness of each layer of the film was (A) / (B) / (C) = 60 μm / 50 μm / 10 μm (total 120 μm). An extruded multilayer film was obtained.

(Comparative Example 5)
The thickness of each layer of the film was (A) / (B) in the same manner as in Example 5 except that LLDPE was used as the resin for the resin layer (A) and LLDPE was used as the resin for the resin layer (C). ) / (A) / (C) = 40 μm / 50 μm / 20 μm / 10 μm (total 120 μm) to produce a co-extruded multilayer film, thereby obtaining a co-extruded multilayer film.

(Comparative Example 6)
Using the same resin as that used in Comparative Example 4 for each resin layer, the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 10 μm / 10 μm (total 30 μm). A coextruded multilayer film was prepared as described above to obtain a coextruded multilayer film. Next, the surface of the resin layer (A) of the coextruded multilayer film was subjected to corona discharge treatment so that the surface energy was 36 mN / m.

  A biaxially stretched polyethylene terephthalate film (thickness 12 μm) was bonded to the surface of the resin layer (A) of the coextruded multilayer film obtained above by dry lamination to obtain a laminate film. At this time, as a dry lamination adhesive, a two-component curable adhesive (polyester adhesive “LX63F” and a curing agent “KP90”) manufactured by Dainippon Ink & Chemicals, Inc. was used.

  The following tests and evaluations were performed using the coextruded multilayer films obtained in Examples 1 to 7 and Comparative Examples 1 to 6.

(Evaluation of easy cutability)
The coextruded multilayer film obtained above was cut into test pieces each having a size of 63 mm × 76 mm in accordance with JIS K7128, and the tear strength was measured using an Elmendorf tear tester (manufactured by Tester Sangyo Co., Ltd.). It was measured. The tear strength was measured in the extrusion direction (longitudinal (MD) direction) during film formation of the coextruded multilayer film and in the direction perpendicular to this direction (transverse (CD) direction). The tearability was evaluated from the obtained tear strength according to the following criteria.
○: Tear strength is less than 450.
Δ: Tear strength is 450 or more and less than 550.
X: Tear strength is 550 or more.

(Evaluation of straight cut performance)
The co-extruded multilayer film obtained above is cut into test pieces each having a size of 10 cm × 10 cm, a notch for tearing is put in the center position of the vertical and horizontal sides of the film, a constant force and a constant speed. Torn by hand. From the deviation of the tearing part of the test piece, the linear cutability was evaluated according to the following criteria.
○: The deviation of the tearing portion is less than 1 cm from the center.
(Triangle | delta): The shift | offset | difference of the tearing part is 1 cm or more and less than 2 cm from the center.
X: The shift | offset | difference of the tearing part is 2 cm or more from the center.

(Evaluation of secondary formability)
The co-extruded multilayer film obtained above was subjected to secondary forming by vacuum forming into a cylindrical shape having a diameter of 5 cm and a depth of 3 cm, respectively, to obtain a deep-drawn molded product. The molding state of the obtained molded product and the pinhole state of the bottom corner were visually observed, and the moldability was evaluated according to the following criteria.
○: Appearance is uniform and there is no pinhole.
X: Appearance is uneven or pinholes are generated.

(Evaluation of pinhole resistance)
Each of the coextruded multilayer films obtained above was bent 200 times at room temperature using a gelbo flex tester (manufactured by Tester Sangyo Co., Ltd.), and the following criteria were obtained from the number of pinholes generated in the bent portion. Was used to evaluate pinhole resistance.
○: No pinhole.
X: There is a pinhole.

(Easy peel evaluation)
The surfaces of the resin layers (C) of the coextruded multilayer film or laminate film obtained above were overlapped, and heat sealing was performed under the conditions of a heat sealing temperature of 160 ° C., a sealing pressure of 0.2 MPa, and a sealing time of 1 second. Next, the heat-sealed film was naturally cooled at 23 ° C., and then cut into a 15 mm-wide strip to obtain a test piece. This test piece was subjected to a tensile tester (A & 90 ° peeling was performed at a rate of 300 mm / min, and the heat seal strength was measured. From the value of the obtained heat seal strength, the easy peel property was evaluated according to the following criteria.
○: Heat seal strength is in the range of 2 to 15 N / 15 mm.
X: Heat seal strength is outside the range of 2 to 15 N / 15 mm.
* I think that it is better to specify the heat seal strength value in the table.

  The results obtained above are shown in Tables 1 and 2.

  From the results of Examples 1 to 7 in Table 1, the following was found.

  From the results of Examples 1 to 6, the coextruded multilayer film of the present invention can be torn with a small force, not only in the vertical direction but also in the horizontal direction, even if the film thickness is 120 μm, It was also found that it has easy peel properties and is excellent in easy opening. Moreover, since it is excellent in linear cut property, it has the stable opening property. Furthermore, it has been found that it has secondary formability capable of producing a deep-drawn molded product and is excellent in pinhole resistance. It was also found that the tear strength can be controlled without changing the COP concentration by changing the content ratio of LDPE and LLDPE used in each of the resin layers (A) to (C).

  From the results of Example 7, it was found that the coextruded multilayer film of the present invention can be excellent in easy-cut property, straight-line cut property, and easy peel property even when used as a sealant film for a laminate film.

  From the results of Comparative Examples 1 to 6 in Table 2, the following was found.

  The coextruded multilayer film of Comparative Example 1 is an example in which the content ratio of the cyclic olefin resin (COP) in the resin layer (B) is 8% by mass, which is less than 10% by mass, It was found that the straight line cutability in the vertical direction and the horizontal direction was insufficient.

  The coextruded multilayer film of Comparative Example 2 is an example in which the content ratio of the cyclic olefin resin (COP) in the resin layer (B) is 40% by mass exceeding 30% by mass, but the pinhole resistance is insufficient. It turns out that.

  The coextruded multilayer film of Comparative Example 3 is an example in which the content ratio of butene-1 polymer (PB-1) in the resin layer (C) is 40% by mass exceeding 30% by mass, but the heat seal strength is It was found that practical heat sealing was not possible because it was too small.

  The coextruded multilayer film of Comparative Example 4 is an example in which the butene-1 polymer (PB-1) was not used in the resin layer (C), but the heat seal strength was high and the easy peel property was insufficient. I found out.

  The coextruded multilayer film of Comparative Example 5 is an example in which a butene-1 polymer (PB-1) is not used in the resin layer (C) and the multilayer film has a four-layer structure, but the heat seal strength is high. It was found to be high and easy peelability was insufficient.

The example of Comparative Example 6 is an example in which the thickness of the same co-extruded multilayer film as in Comparative Example 4 is 30 μm and is used as a sealant film for a laminate film. It was found that the heat seal strength was high and the easy peel property was insufficient.


Claims (6)

  1. Resin layer (A) comprising low density polyethylene (a1) and / or linear low density polyethylene (a2), and low density polyethylene (b1) and / or linear low density polyethylene (b2) 70 to 90% by mass And a resin layer (B) containing 10 to 30% by mass of a cyclic olefin resin (b3), 70 to 90% by weight of low density polyethylene (c1) and / or linear low density polyethylene (c2), and butene A resin layer (C) containing 10 to 30% by weight of a -1 polymer (c3), in the order of (A) / (B) / (C), or (A) / (B) / (A) The thickness of the film is 100 to 300 μm and the thickness of the resin layer (C) is 10 to 30 μm.
    The low-density polyethylene (a1), (b1), and (c1) has a density of 0.915 to 0.930 g / cm 3 and is a co-extruded multilayer film for secondary molding .
  2. The co-extruded multilayer film for secondary molding according to claim 1, wherein the cyclic olefin resin (b2) is a norbornene polymer.
  3. The coextrusion for secondary molding according to claim 1 or 2, wherein the linear low density polyethylene resins (a2), (b2) and (c2) are ethylene-butene-1 copolymers produced by a metallocene catalyst. Multilayer film.
  4. The thickness of the resin layer (B) is coextruded a 20-5 0% thickness any one coextruded multilayer film for secondary molding as claimed in claim 1 to 3, the multilayer film.
  5. The density of the linear low density polyethylene (a2), (b2) and (c3) is 0.916 to 0.950 g / cm. 3 The co-extruded multilayer film for secondary molding according to claim 3 or 4.
  6. A bottom material obtained by deep drawing the co-extruded multilayer film for secondary forming according to any one of claims 1 to 5.
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